[sgqwonkian]

The 1.22 patch makes it so that haveitem detects passengers. If you haven't downloaded the patch, there's no way to make it notice passengers.

To make it detect a specific passenger, have the STR0 for your haveitem be the name of the passenger file, such as ps_calamb, for example.

To make it detect passengers in general, you'd need to either do multiple haveitem CONDITIONs, or give all passengers a KEYS in common. Then have the STR0 for your haveitem be the same as that KEYS entry.

If you do go the KEYS route, bare in mind that the game won't randomly generate two items with the same KEYS entry. With the existing passengers, that's no problem, since they don't generate randomly, and are instead made specifically by quests. If, however, you wanted a randomly-occurring non-quest-derived passenger, the KEYS would matter.